Fluid power generator

ABSTRACT

In a fluid power generator system using operative fluid energy, a measured tip speed ratio and a reference tip speed ratio are compared with each other. If the measured tip speed ratio is smaller than the reference tip speed ratio, a generator is placed in a no-load state, thereby restoring the number of rotations of the wing axial shaft to the number of rotations corresponding to the reference tip speed ratio. Further, the operation of the generator is controlled on the basis of the tip speed ratio calculated from the flow rate of the fluid, thereby providing a maximum output for each flow rate. In this way, a change in the flow rate and number of rotations can be appropriately dealt with and the maximum output for each flow rate of the operative fluid can be dealt with, thereby increasing a quantity of generated power.

TECHNICAL FIELD

This invention relates to a fluid power generator system for convertingoperative fluid energy such as wind into rotary energy to be used aselectric energy.

BACKGROUND ART

As a fluid power generator system which uses the operative fluid energyas a driving source to generate electric power, a wind vane generatorusing wind power energy has been proposed. In the field of this windvane generator, the wind power energy, a demand of using wind powerenergy in a wide range from a breeze to strong wind has been enhanced.

The wind power generator system includes a generator which is driven byrotation of a wind turbine and a battery which is charged by powersupply from the generator. In this wind power generator system, powercan be supplied to loads such as an electric device while the battery ischarged by the rotation of the wind turbine.

In the above conventional wind power generator system, even when thereis a breeze blowing, the generator which serves as load for the windturbine remains in a coupled state. Namely, the wind power generatorsystem does not have a function of automatically decoupling thegenerator according to a change in the wind and coupling the windturbine after the rotation of the wind turbine has been restored.

Where there is strong wind when the battery is in a full-charged state,the wind turbine is mechanically braked or the output from the generatoris short-circuited to stop power generation, thereby preventingexcessive rotation of the wind turbine. However, the moment that theoutput from the generator is short-circuited, the generator may becomeno load and the rotation of the wind turbine may become excessive.

An object of this invention is to provide a fluid power generator systemwhich can deal with changes in the flow rate of an operative fluid suchas wind and number of rotations (rotational speed) by controlling thetip speed ratio of a generator, thereby acquiring a maximum output at aspecific flow rate.

DISCLOSURE OF THE INVENTION

In order to attain the above object, in accordance with this invention,there is provided a fluid power generator system comprising a generatorcoupled with a wing axial shaft which is rotated by operative fluidenergy as a driving source and a load device including a batteryconnected to the generator, comprising a comparing means for comparingan measured tip speed ratio and a reference tip speed ratio, themeasured tip speed ratio being calculated by a flow-rate signal based ona flow-rate of the operative fluid and a number of rotations signalbased on the number of rotations of the wing axial shaft, and thereference tip speed ratio providing a maximum conversion efficiency ofthe operative fluid energy in the fluid power generator system; and

-   -   a load control means for on/off controlling the load device so        that if the measured tip speed ratio is smaller than the        reference tip speed ratio as a result of comparison by the        comparing means, the generator is placed in a no-load state,        thereby restoring the number of rotations of the wing axial        shaft to the number of rotations corresponding to the reference        tip speed ratio.

Preferably, the load control means places the generator in the no-loadstate if the measured tip speed ratio is smaller than the reference tipspeed ratio as a result of comparison by the comparing means andcontinues the no-load state until the number of rotations is restored tothe number of rotations corresponding to the reference tip speed ratio,thereby dealing with a change in the number of rotations of the windaxial shaft.

Preferably, when the battery of the load device is fully charged, powersupply to the battery is stopped by an output from an excessive voltagedetecting unit and a dummy load is connected to the generator.

Further, there is provided a fluid power generator system comprising agenerator coupled with a wing axial shaft which is rotated by operativefluid energy as a driving source, comprising a control means forcontrolling the operation of the generator on the basis of a measuredtip speed ratio which is calculated by a measured flow-rate of theoperative fluid and a measured number of rotations of the wing axialshaft, thereby providing a maximum output for a specific flow-rate ofthe operative fluid.

Preferably, the control means constantly controls the operation of thegenerator on the basis of a measured tip speed ratio which is calculatedfrom a measured flow rate of the operative fluid and higher number ofrotations exceeding an output peak value at the measured number ofrotations of the axial shaft, so that a maximum output for the specificflow rate of the fluid is obtained by load given to the wing axialshaft.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing an embodiment of this invention;

FIG. 2 is a block diagram of a control circuit;

FIG. 3 is a conceptual view showing a control system;

FIG. 4 is a characteristic view of power generation efficiency versus atip speed ratio; and

FIG. 5 is a characteristic view showing an example of control of the tipspeed ratio.

BEST MODE FOR CARRYING OUT THE INVENTION

Now referring to the drawings, an explanation will be given of anembodiment of this invention.

FIG. 1 shows an arrangement of the wind power generator which convertswind power energy serving as operative fluid energy into rotary energyto be used as electric energy;

In FIG. 1, a wind turbine 1 includes e.g. linear blades 2 which areintegrally attached to a wing axial shaft 4 by upper and lowersupporting blades 3, respectively. The wing rotary shaft 4 is coupledwith a generator 5 such as a synchronous generator (three-phase AC)through a transmission. The wing axial shaft 4 is provided with a brake7 and a revolving number detecting unit 8 for the number of rotations ofthe wind turbine 1.

The revolving number detecting unit 8 serves to detect the number ofrotations of the wind turbine 1 with the aid of a tachometer generatorand a photosensor and photovoltaic converter. This detectednumber-of-revolution signal is supplied to a control circuit 9. The windspeed is detected by a wind speed detecting unit 10 such as a wind speedindicator, and the detected wind speed signal is supplied to a controlcircuit 9.

FIG. 2 shows the main portion of the control circuit 9 in FIG. 1. Thenumber of rotations of the wing axial shaft 4 is detected by the numberof rotations detecting unit 8. The number of rotations signal of thewing axial shaft is supplied to a tip speed ratio calculating circuit 91for calculating an measured tip speed ratio in the control circuit 9.The wind speed signal detected by the wind speed detecting unit is alsosupplied to the measured tip speed ratio calculating circuit 91.

The measured tip speed ratio calculating circuit 91 calculates themeasured tip speed ratio from the number of rotations signal based onthe number of rotations of the wing axial shaft 4 and the wind speedsignal based on the wind speed. The measured tip speed ratio is suppliedto a comparing circuit (comparing means) 92. The comparing circuit 92also receives a reference tip speed ratio. The reference tip speed ratiois previously set at a value where the conversion efficiency of windpower is maximum in the wind power generator system in FIG. 1.

On the basis of a comparison result between the measured tip speed ratioand the reference tip speed ratio, the comparing circuit 92 supplies acontrol signal to a load control circuit 96. As a result of comparison,if the measured tip speed ratio is smaller than the reference tip speedratio, the comparing circuit 92 issues a command of turning off abattery 111 of the load device 11 and an electric contact of thegenerator 5 to a load control circuit 96. The load control circuit 96causes an exchanger 113 to place the generator 5 in a no-load state. Theoperation of placing the generator 5 in the no-load state can be easilyimplemented using an unload valve.

In this way, if the measured tip speed ratio is smaller than thereference tip speed ratio, the generator 5 is placed in the no-loadstate to reduce the load for the wing axial shaft 4. This operation willbe continued until the number of rotations of the wind axial shaft isrestored to that corresponding to the reference tip speed ratio. Thus,the start of the rotation of the wind turbine 1 is greatly acceleratedso that the wind power generator system can sensitively deal withchanges in the wind speed and number of rotations. This improves thepower generation efficiency and hence the net working rate of the windpower generator system.

In the load device 11, if the battery 111 is in a fully-charged state,in response to the output from an excessive voltage detecting circuit112, the exchanger 113 stops the power supply to the battery 111 andconnects a dummy load 114 to the generator 5. Thus, the generator 5 isnot placed in the no-load state so that suitable braking is applied.Accordingly, the wing axial shaft 4 coupled with the generator 5, i.e.the wind turbine 1 is prevented from falling into an excessive rotaryrange so that the linear blades 2 of the wind turbine 1 is preventedfrom being damaged. The dummy load 114 may be given by turning on lightsor operating a connected heater for heat recovery. Thus, the surpluspower can be effectively used until the full-charged state of thebattery 111 is dissolved.

In the embodiment shown in FIG. 1, the operation of each of thegenerators A to G can be controlled on the basis of the tip speed ratioβ (β=number of rotations N or rotor tip speed/wind speed V) which hasbeen calculated from the wind speed V and the number of rotations N ofthe wind rotary shaft 4. The rotor tip speed is represented by 2πRN (Ris a diameter). Assuming that 2πR is constant, the rotor tip speed canbe replaced by the number of rotations N. Specifically, as shown in FIG.5, when the generator (e.g. A) is coupled with the wind rotary shaft 13at a higher number of rotations, i.e. point (b) (β=4.5) exceeding a peakvalue, i.e. point (a) of the wind speed V=9 m/sec., the generator servesas a load for the wind rotary shaft 13. As a result, the number ofrotations N of the wing rotary shaft 13 decreases like ancounterclockwise arrow in FIG. 5 and reaches the peak value, i.e. point(a) of the output.

Because the maximum efficiency of the wind turbine 1 is actuallyobtained at the tip speed ratio β=4.5, the operation should be made inthe vicinity of β=4.5. In this way, by controlling each of thegenerators A to G on the tip speed ratio, as seen from FIGS. 5 and 6,these generators A to G can be operated at the peak value, i.e. point(a) so that the maximum output according to a specific wind speed can beobtained.

FIG. 3 is a conceptual view showing the control system of the wind powergenerator system shown in FIG. 1. This control system has threefunctions of a start-up and accelerating function, tip speed ratiocontrol function and a braking function. The wind speed is detected by awind speed detecting unit 10 which may be an anemometer. The number ofrotations of the wind turbine 1 is detected by the number of rotationsdetecting unit 8 which includes a tachometer generator and measurementby a photosensor and photovoltaic converter. These wind speed signal andnumber of rotations signal are processed by a voltage comparator 12 anda logic circuit 13 and are produced as control signals.

The start-up and accelerating function is to operate a start motor whenthe wind speed exceeds a certain minimum value and the tip speed ratioof the wind turbine 1 is lower than a prescribed value. The tip speedratio control function is to operate an unload valve to place thegenerator in a no-load state when the tip speed ratio is lower than amaximum value. This state continues until the number-of-revolution ofthe wind turbine 1 is restored to the reference number of rotations todeal with a change in the number of rotations.

The braking function includes two functions inclusive of a normalbraking function and an emergency braking function. The normal brakingfunction is to operate an air brake when the wind speed exceeds adesigned maximum value. The emergency braking function is to operate theair brake when the wind speed exceeds the designed maximum value andalso the detected signals from the two number of rotations detectingunits 8 are abnormal.

The braking system includes a braking system by a cut-out wind speed andan emergency braking system by excessive rotation by the wind turbine 1.Particularly, the braking system has a function of self-diagnosis fordetecting abnormality of the number of rotations which is important fromthe viewpoint of safety.

This invention should not be limited to the above embodiment which hasbeen explained in the wind power generator system. The fluid powergenerator system according to this invention can be applied to a waterpower or other generating system. This invention can be implemented incombination with solar power generation as a hybrid power generatorsystem.

The fluid power generator system can be equipped with control meanswhich can monitor various observed data indicative of a generated power,number of rotations, flow rate, etc. or video data capable of monitoringan operating status by using a communication means such as satellitecommunication or internet on any site on the earth, thereby implementingthe operation in bi-directional communication.

On the side wall of a high building, the axial shaft may be located notvertically but horizontally. In place of the supporting blade, a diskserving as a supporting portion can be employed.

INDUSTRIAL APPLICABILITY

In accordance with the invention described in claim 1, in the fluidpower generator, a change in the flow-rate and number of rotations canbe appropriately dealt with so that the power generation efficiency canbe improved. This improves the operation efficiency of the fluid powergenerator system and increases the generated power.

In accordance with the invention described in claim 2, when the flowrate becomes lower than the reference level, the generator isautomatically placed in the no-load state so that the burden for thewing axial shaft can be relaxed and the no-load state can be continueduntil the number of rotations is restored to the reference number ofrotations. Therefore, a change in the flow-rate and number of rotationscan be appropriately dealt with so that the power generation efficiency.This improves the operation efficiency of the fluid power generatorsystem and increases the generated power.

In accordance with the invention described in claim 3, since the batteryis fully charged, power supply to the battery from the generator isstopped and the dummy load is coupled with the generator. Therefore, thegenerator is not placed in the no-load state so that suitable, electricbraking can be applied. Thus, the rotating unit at high speed rotationcan be prevented from being damaged. Further, by using the heater or thelike as the dummy load, the surplus power can be effectively used untilthe fully-charged state of the battery is released.

In accordance with the invention described in claim 4, by controllingthe operation of the generator on the basis of the tip speed ratio whichis calculated from the flow rate and the number of rotations, themaximum output for each flow rate of the operative fluid can beobtained. This improves the operation efficiency of the fluid powergenerator system and increases the generated power.

In accordance with the invention described in claim 4, by controllingthe operation of the generator on the basis of the tip speed ratio whichis calculated from the flow rate of the operative fluid and the highernumber of rotations exceeding an output peak value at the measurednumber of rotations of the axial shaft, the maximum output for each flowrate of the operative fluid can be obtained. This improves the operationefficiency of the fluid power generator system and increases thegenerated power.

1. A fluid power generator system including a generator coupled with awing axial shaft which is rotated by operative fluid energy as a drivingsource and a load device including a battery connected to the generator,the fluid power generator system comprises: a comparing means forcomparing an measured tip speed ratio, said measured tip speed ratiobeing calculated by a flow-rate signal based on a flow-rate of theoperative fluid and a number of rotations based on the number ofrotations of said wing axial shaft, and said reference tip speed ratioproviding a maximum conversion efficiency of the operative fluid energyin said fluid power generator system; and a load control means foron/off controlling said load device so that if said measured tip speedratio is smaller than said reference tip speed ratio as a result ofcomparison by said comparing means, said generator is placed in ano-load state, thereby restoring the number of rotations of said wingaxial shaft to the number or rotations corresponding to said referencetip speed ratio said load control means being independent means forcontrolling a load which is applied to the generator; and a brakingincluding a revolving number detecting unit for detecting the number ofrevolutions of said wing axial shaft and a brake unit for braking therotation of the wing, said braking means operating the brake when theflow-rate of the operative fluid exceeds a designated maximum value orwhen a detected signal form the revolving number detecting unit isabnormal.
 2. A fluid power generator system according to claim 1,wherein said load control means places said generator in the no-loadstate if said measured tip speed ratio is smaller than said referencetip speed ratio as a result of comparison by said comparing means andcontinues the no-load state until said number of rotations is restoredto the number of rotations corresponding to said reference tip speedratio, thereby dealing with a change in the number of rotations of saidwing axial shaft.
 3. A fluid power generator system according to claim1, wherein when the battery of said load device is fully charged, powersupply to said battery is stopped by an output form an excessive voltagedetecting unit and a dummy load is connected to said generator.
 4. Afluid power generator system having a generator coupled with a wingaxial shaft which is rotated by operative fluid energy as a drivingsource, said fluid power generator comprising a control means forcontrolling the operation of said generator on the basis of a measuredtip speed which is calculated by a measured flow-rate of the operativefluid and a measured number of rotations of said wind axial shaft,thereby providing a maximum output for each flow-rate of the operativefluid; and a braking means including a revolving number detecting unitfor detecting the number of rotations of said wing axial shaft and abrake for braking the rotation of the wing, the braking meanscontrolling the rotational speed of the wiring axial shaft.
 5. A fluidpower generator system according to claim 4, wherein said control meansconstantly controls the operation of said generator on the basis of ameasured tips speed ratio which is calculated from a measured flow ratof the operative fluid and higher number of rotations exceeding anoutput peak value at the measured number of rotations of the axialshaft, so that a maximum output for each flow rate of the fluid isobtained by a load given to said wing axial shaft.
 6. A fluid powergenerator system according to claim 1, wherein when the battery of saidload device is fully charged, power supply to said battery is stopped byan output form an excessive voltage detecting unit and a dummy load isconnected to said generator.